These lines are an example of a couplet. A couplet is a pair of lines in a poem that usually rhyme and have the same meter. In this particular couplet, the rhyme scheme is AABB. The poet uses this couplet to express the idea that if their beliefs or feelings are proven false, then they declare that they have never written anything and that no one has ever truly loved. This couplet is often attributed to William Shakespeare and is found in his Sonnet 116.
